KR102393740B1 - Control of the amplitude and phase of diffraction orders using a polarized target and polarized illumination - Google Patents

Abstract

Metrology scatterometry targets, optical systems and corresponding metrology tools, and measurement methods are provided. The target and/or optical system generates a phase shift of 180° between the 0th order diffraction signals upon illumination of the scatterometry target, whereby the 1st order diffraction signal relative to the 0th order diffraction signal from the scatterometry target designed to improve For example, a target may be designed to respond to polarized illumination by creating a first phase shift between the zeroth order diffraction signals upon illumination, and optical systems illuminate the target with polarized illumination and analyze the resulting diffraction signal Thus, it may be designed to cause a second phase shift between the 0th order diffraction signals upon illumination. With a phase shift between 0° and 180°, the phase shift is added up to 180° to cancel the 0th order diffraction signal.

Description

Control of the amplitude and phase of diffraction orders using a polarized target and polarized illumination

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of US Provisional Application No. 62/264,514, filed December 8, 2015, which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION The present invention relates to the field of metrology, and more particularly to the control of polarization targets and corresponding polarizations in optical systems of metrology tools.

Current methods for optical overlay measurements rely on two main techniques, Imaging and Scatterometry. In imaging, the position of a periodic target is measured in the field of view of the optical system, and an overlay (OVL) is inferred from the position of the target printed in different layers. Scatterometry uses interference between electromagnetic (EM) waves scattered by periodic overlay marks (targets with periodic structures) printed on different layers to infer the relative displacement of the layers. In either case, the control over the amplitude and phase of the diffraction order of the scattered EM wave may have a decisive effect on the accuracy and precision of the overlay measurement.

The following is a brief summary to provide an initial understanding of the present invention. The Summary does not necessarily identify key components nor limit the scope of the invention, but merely serves to introduce the following description.

One aspect of the present invention provides that a scatterometry target is designed and/or instrumented to produce a 180° phase shift between zeroth order diffraction signals upon illumination of the scatterometry target. There is provided a method comprising enhancing a first order diffraction signal with respect to a zero order diffraction signal from a scatterometry target having a coarse pitch by configuring the optical system of the tool.

These, additional, and/or other aspects and/or advantages of the present invention are set forth in the detailed description that follows; Where possible, it can be inferred from the detailed description; and/or learnable by practice of the present invention.

In order to better understand an embodiment of the invention and to show how the embodiment may be practiced, reference will now be made to the accompanying drawings, purely by way of example, in which like reference numerals refer throughout to corresponding elements or sections. indicates
In the attached drawing,
1A is a high-level schematic diagram of a metrology system 105 implementing polarization phase control to cancel a zero-order diffraction signal, in accordance with some embodiments of the present invention.
1B, 1C, 2A, and 2C are high level schematic diagrams of scatterometry targets, in accordance with some embodiments of the present invention.
3 is a high level schematic diagram of an optical system, in accordance with some embodiments of the present invention.
4 is a high-level flow diagram illustrating a method, in accordance with some embodiments of the present invention.

In the following description, various aspects of the present invention are set forth. For purposes of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the present invention. However, it will also be apparent to one skilled in the art that the present invention may be practiced without the specific details provided herein. Also, well-known features may be omitted or simplified in order not to obscure the present invention. With specific reference to the drawings, it is provided that the details shown are illustrative only and for purposes of descriptive discussion of the invention, what is believed to be the most useful and easily understood description of the principles and conceptual aspects of the invention. It is emphasized that it is presented to In this regard, no attempt is made to show structural details of the invention in more detail than are necessary for a fundamental understanding of the invention, and the description of the drawings will help those skilled in the art understand how the various aspects of the invention may be embodied in practice. will make it clear

Before at least one embodiment of the present invention is described in detail, it is to be understood that the present invention, in its application, is not limited to the details of construction and arrangement of components set forth in the following description or shown in the drawings. The invention is applicable not only to combinations of the disclosed embodiments, but also to other embodiments that may be practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

Unless specifically stated otherwise, "processing", "computing", "calculating", "determining", "enhancing", as apparent from the following description, Discussions using terms such as, etc., refer throughout this specification to refer to data expressed in physical quantities, such as electronic quantities in registers and/or memory of a computing system, to physical quantities in memory, registers or other such information storage, transmission, or display devices of the computing system. It is recognized that it refers to the operation and/or process of a computer or computing system, or similar electronic computing device, that manipulates and/or transforms other data that is similarly expressed as a quantity.

We show that when target asymmetry is present, the mechanism of target asymmetry amplification is linked to the difference value in topographic phase between the first diffraction orders in the case of scatterometry OVL (from the upper and lower gratings). +1 and -1) and that the mechanism of target asymmetric amplification is linked to the value of the difference in topographical phase between the first and zero diffraction orders in the case of imaging OVL (±1 and 0 from the upper and lower gratings). ) was found. Some hardware (HW) possibilities for terrain phase control may greatly improve the accuracy of OVL measurements.

The inventors have further discovered that another relatively common measurement problem arises when there is a large difference between an amplitude of zero and other diffraction orders, resulting in very low image contrast. The same problem appears in scatterometry OVL when the amplitude of the first diffraction order from the two measured layers differs by more than the order of magnitude. In this case, reducing the amplitude of the appropriate diffraction order can greatly improve the precision and accuracy of the measurement.

The following related documents, which are hereby incorporated by reference in their entirety, may also be incorporated with the present disclosure to achieve mutual improvement in accuracy, and such combinations are considered a part of the present invention. (i) WIPO Patent Publication No. PCT/US15/62523 describes deriving a partially continuous dependence of metrology metric(s) on recipe parameter(s), analyzing the derived dependence, determining a metrology recipe according to the analysis, and measuring It discloses determining the measurement(s) according to the determined recipe. (ii) US Patent Application No. 62/222724 discloses different approaches (mainly HW options) for terrain topology control, and provides practical criteria for selecting the most appropriate recipe settings. (iii) The internal document discloses controlling the amplitude and phase of the zero diffraction order to improve the precision and accuracy of overlay measurements. For example, this document discloses the implementation of HW options for zero diffraction order control, including the use of leak blockers, adaptive optical elements, and interference control. This disclosure focuses on providing an additional level of control over the diffraction order parameters using a polarization target and a polarization control HW. Also, although the present disclosure uses relatively simple HW, is associated with a target design procedure, and is illustrated in a non-limiting manner with respect to a first diffraction order signal, it may be applied to any diffraction order.

Metrology scatterometry targets, optical systems and corresponding metrology tools, and measurement methods are provided. The target and/or optical system generates a phase shift of 180° between the 0th order diffraction signals upon illumination of the scatterometry target, whereby the 1st order diffraction signal relative to the 0th order diffraction signal from the scatterometry target designed to improve For example, a target may be designed to respond to polarized illumination by creating a first phase shift between the zeroth order diffraction signals upon illumination, and optical systems illuminate the target with polarized illumination and analyze the resulting diffraction signal Thus, it may be designed to cause a second phase shift between the 0th order diffraction signals upon illumination. With a phase shift between 0° and 180°, the phase shift is added up to 180° to cancel the zero-order diffraction signal.

1A is a high-level schematic diagram of a metrology system 105 implementing polarization phase control to cancel a zero-order diffraction signal, in accordance with some embodiments of the present invention. Metrology system 105 includes a metrology tool having a scatterometry metrology target 100 and an optical system 150 . The scatterometry metrology target 100 has a coarse pitch and is configured to create a first phase shift 121 between the zeroth order diffraction signals upon illumination of the target. The optical system 150 illuminates the target 100 by two vertically polarized illumination components and analyzes the resulting diffraction signals in two vertically polarized directions that complement the two vertically polarized illumination components to illuminate the target. and generate a second phase shift 122 between the zero-order diffraction signals at the time. The sum of the first phase shift 121 and the second phase shift 122 is 180° to cancel the zero-order diffraction signal. Figure 1a schematically shows the polarization of the diffraction order, where the 0th order component is canceled by the addition of 180° phase, while the 1st diffraction order is the +1st order component with the addition of the −1st order component with 180° phase added. is improved by Metrology system 105 may be configured to cancel the zero-order diffraction signal, as described below, by target design alone, optical system design alone, or combined adjustments to the target design and optical system design.

1B is a high level schematic diagram of a scatterometry target 100 in accordance with some embodiments of the present invention. The target 100 is configured to change the polarization of the diffraction signal with respect to illumination and is therefore referred to as a polarization target. The target 100 may be measured to provide a diffraction signal in connection with an optical system configured to provide robust hardware polarization control (see system 150 below as an exemplary, non-limiting option). The target 100 has a coarse pitch P1 well determined by a metrology tool (eg 1000-2000 nm). The target 100 is configured to create a 180° phase shift between the 0th order diffraction signals upon illumination of the target, by having the vertically polarizing elements 103 at half coarse pitch to produce a 180° phase shift. . A portion 110 , eg half of, of the coarse pitch region is divided in one direction (eg X direction) by a fine, unresolved pitch P2 , while another portion 115 , eg For example, the other half of the coarse pitch region is divided into the same fine division pitch P2 in a direction perpendicular to the first direction (eg, Y direction). As a result, since the target unit cells 101 and 102 are shifted by half the pitch P1, the first diffraction order signal from the polarized illumination in the X and Y directions has a phase difference of 180° (π). Therefore, the 0th order signals from cells 101 and 102 cancel each other out, and the 1st order signals from cells 101 and 102 have an inherent 180° (π) between the +1 diffraction order signal and the -1 diffraction order signal. They are summed due to phase. For pitches greater than 2λ, a second diffraction order and a higher diffraction order may be included, and a phase difference may also be used to remove/enhance those pitches (eg, a 180° phase difference even diffracts remove orders, enhance odd diffraction orders).

1C is a high level schematic diagram of a scatterometry target 100 , in accordance with some embodiments of the present invention. The target 100 may be partitioned in both directions to improve process compatibility. The vertically polarized elements 103 may be divided into fine pitches. In FIG. 1C , an additional division with pitch P ₃ is added to the target design shown in FIG. 1B . In order to avoid the secondary polarization effect and the destruction of symmetry between the target sub-cells 101 and 102, the two fine pitch divisions may be performed with the same pitch in the X and Y directions.

Target 100 may be constructed by selecting target pitches (eg, any of P ₁ , P ₂ , P ₃ ), field fill factor (duty cycle), segmentation type, and the like. In the case of side-by-side imaging targets, the use of non-resolved periodic structures in one layer to measure periodic structures in other layers may be used to construct additional features to optimize target design (e.g., lower grating measurements). for the use of undissolved periodic structures in the upper floors and vice versa)

2A and 2B are high-level schematic diagrams of a scatterometry target 100 , in accordance with some embodiments of the present invention. The target 100 includes an initial non-polarizing structure 90 (with a resolved pitch P1) and at least one polarizing structure 146 (finer, unresolved pitch P ₂ < P ₁ , also referred to as a dummy structure). at least one additional target layer (145) having For example, additional target layer(s) 145 may be above or below the initial layer 90 (shown in FIGS. 2A and 2B , respectively). The unresolved pitch P2 may be, for example, half of the resolved pitch P ₁ . The unresolved pitch P2 and the position and distance of the layer 145 relative to the layer 90 may be selected to produce a specific first phase shift 121 , which may be 180°, but cancels the zeroth diffraction order. may have other values that are complemented by the second phase shift 122 of the optical system 150 to produce an overall phase shift of 180°. In the manner shown, the unresolved periodic structure in any intermediate or lower layer may be used for target design optimization for side-by-side and grating-over-grating targets.

Unresolved periodic structures 146 in layer 145 change the effective permittivity of the layer in which they are disposed, thus affecting the generation and propagation of diffraction orders within the overall stack. Accordingly, unresolved dummy structures and divisions at pitches close to the design rule pitch may improve the measured target's sensitivity to polarization. The field fill factor of the unresolved dummy structure 145 may also be modified or designed to control the response of the target to the illumination polarization. To avoid possible cross-talk between the target (layer 90) and the dummy structures in the complementary layer (dummy 145), the dummy structural element 146 is oriented orthogonal to the measured target period direction. It may be designed to be divided into The polarizing structure(s) 145 may be divided along a direction perpendicular to the division direction of the initial non-polarizing structure 90 . Accordingly, the additional layer 145 may be partitioned along the Y-direction rather than following the X-direction partitioning shown in FIGS. 2A and 2B .

The target design file of the disclosed scatterometry metrology target 100 is considered part of this disclosure.

3 is a high level schematic diagram of an optical system 150 , in accordance with some embodiments of the present invention. The optical system 150 uses an illumination arm 161 having an illumination source 75 , a polarizer 160 positioned to polarize the illumination (eg, continuously), and wave plate parameters (angle and retardation). thus comprising a first wave plate 165 arranged to determine a phase shift 122A between two orthogonal polarization directions. The optical system 150 directs illumination through an objective lens 70 on a target 100 on a wafer 60 and collects a diffraction signal from the target 100 passing through the objective lens 70 in a collection arm. and a (non-polarized or polarized) beam splitter 80 configured to direct to 171 . The collection arm 171 includes a second wave plate 175 of a collection polarization angle 122B, an analyzer 170 , and a detector 85 . Illumination and collection polarization angles 122A, 122B may be configured to provide a second phase shift 122 depending on the type of target and system configuration.

For example, using the polarizing target 100 and half-wave plates 165 and 175 shown in FIGS. 1B and 1C , since an overall phase shift of 180° is provided by the target as described above, It is sufficient to say that the angles 122A and 122B are equal (eg, 45°). In another embodiment, using the polarizing target 100 shown in FIGS. 2A and 2B , the angles 122A, 122B are a first phase shift provided by the addition of the layer 145 to the non-polarizing target 90 . Suffice it to say that it may be different to provide a second phase shift 122 to be added to 121 .

Polarizing beam-splitter 80 may be used in place of or in addition to wave plates 165 , 175 , or alternatively or complementary, any optical element may be used to provide a controllable phase shift. For example, using a polarizing beam-splitter 80 , the optical system 150 separates the optical path of the two vertically polarized light and light between the two polarized light by adding a phase retarder or any other optical element. It is configured such that control over the phase of the diffraction order can be achieved by providing a path difference, also combining both polarizations together, and using an additional beam-splitter.

Optical system 150 may include a neutral density (ND) filter in one of optical paths 161 , 171 and configured to control the relative amplitude of polarization.

In some embodiments, only one of the wave plates 165 , 175 may be used to provide the second phase shift 122 . In some embodiments, polarizer 160 and analyzer 170 may be configured to provide and receive linearly polarized illumination and diffraction signals, respectively, without the use of any wave plates 165 and 175 . For example, polarizer 160 and analyzer 170 may be set at angles of 45° and 135°, correspondingly, to measure targets such as those shown in FIGS. 1B and 1C . Accordingly, the optical system 150 may be configured to provide full 0th order diffraction cancellation and 1st diffraction order amplitude doubling. Figure 3 is very general and robust allowing complete suppression of the zero diffraction order, with all lobes due to the finite target size, which makes the system advantageous with respect to using a blocker in the pupil plane as in the prior art; An optical scheme is shown. In certain embodiments, the inventors have found that full zero-order suppression in combination with quasi-normal illumination provides the best measurement conditions from both an accuracy and precision standpoint.

Polarizer 165 in illumination path 161 and analyzer 170 in collection path 171 may be configured to control a weighting factor of each polarization of the combined signal. The target 100 may be configured to provide great sensitivity of the target response to polarization differences, to enhance the first-order diffraction signal as well as to improve differentiation between different diffraction orders. Further, the optical system 150 and target 100 control the amplitude of the zero diffraction order without significantly affecting the amplitude of the first diffraction order, and/or control the phase between the zero diffraction order and the first diffraction order. It may be configured as described herein to The inventors have found that in the former case an improvement in imaging contrast is achieved, whereas in the latter case an improvement in imaging accuracy is achieved. In scatterometry (eg, SCOL-scatterometry overlay), optical system 150 and target 100 control the phase between first diffraction orders to improve sensitivity and accuracy. It may also be configured to In the case of scatterometry targets, different layers of target cell systems may be designed to provide different responses to changes in polarization direction.

A metrology system that combines the optical system 150 and the scatterometry target 100 of any embodiment is considered part of the present disclosure. In particular, a metrology system is provided, the metrology system comprising: a scatterometry metrology target 100 having a coarse pitch and configured to produce a first phase shift between zero-order diffraction signals upon illumination of the target; Illuminating the target by two vertically polarized illumination components and analyzing the resulting diffraction signals in two perpendicular polarization directions that complement the two vertically polarized illumination components, the second between the 0th order diffraction upon illumination of the target A metrology tool having an optical system (150) configured to generate a phase shift, wherein the sum of the first and second phase shifts is 180° to cancel zero-order diffraction signals.

4 is a high level flow diagram illustrating a method 200, in accordance with some embodiments of the present invention. Method 200 may be implemented at least in part by at least one computer processor, such as in a metrology module. Some embodiments include a computer program product including a computer readable storage medium embodied with a computer readable medium and having a computer readable program configured to perform the relevant steps of the method 200 . Some embodiments include a target design file for each target designed by an embodiment of the method 200 .

Method 200 includes designing a scatterometry target, and/or configuring an optical system of a metrology tool to generate a 180° phase shift between zeroth order diffraction signals upon illumination of the scatterometry target. and enhancing the 1st order diffraction signal for the 0th order diffraction signal from a scatterometry target having a coarse pitch (step 201). For example, method 200 may include combining a first phase shift by a target design and a second phase shift by an optical system configuration, wherein the first and second phase shifts are summed up to 180° (Step 202).

Method 200 may include designing a scatterometry and/or imaging target as well as a corresponding optical system for measuring the designed target. Method 200 includes designing a polarization sensing scatterometry target that enhances a first order diffraction signal in response to polarized illumination (step 205) and using polarization control hardware and polarization target to provide additional diffraction order parameters. It may also include a step of combining (step 210). Method 200 may further comprise generating the designed target(s) (step 230) and/or measuring the designed target(s) in a scatterometric manner (step 235). The method 200 comprises configuring the optical system to separate, using illumination polarization, between signals from orthogonal partitioning regions (step 240), and controlling the polarization phase in the illumination and/or detection light path (step 240). Step 245) may be further included. Method 200 may include configuring an optical system of a metrology tool to separate between signals from orthogonal partitioned regions using illumination polarization (step 242 ).

The method 200 includes a plurality of target elements of at least one periodic structure having at least one coarse pitch resolved by a corresponding scatterometry metrology tool, at least one fine pitch not resolved by a corresponding metrology tool. partitioning (step 220), wherein the fine-segmentation relates to at least two directions within at least some elements and maintains the same zero-order diffraction parameter in the at least two directions. Method 200 may thus include maintaining the same zeroth order diffraction parameters in different directions (step 222 ). Method 200 may design the scatterometry target to have vertically polarized elements at half coarse pitch to produce a 180° phase shift (step 221).

The method 200 may further include dividing the fine segment perpendicular to the at least one still fine pitch (step 225 ).

Method 200 may include performing measurements using two or more polarized illuminations corresponding to at least two fine segmentation directions (step 240), coherently distributing the zero-order diffraction signal for at least two directions. suppressing and enhancing the first-order diffraction signal therefrom (step 250). The method 200 may further include coherently canceling the 0th order diffraction signal and sufficiently adding the 1st order diffraction signal for at least two directions (step 255).

Method 200 comprises the steps of controlling the polarized illumination and diffraction signals using corresponding waveplates (step 260), and possibly assigning and controlling weights of the polarized signals to optimize the collected data (steps). 265) may be further included.

The method 200 includes configuring an optical system of a metrology tool to illuminate a scatterometry target with two vertically polarized illumination components (step 270), comprising the steps of: It may also include analyzing the diffraction signals in two perpendicular polarization directions that complement the illumination component (step 275).

The method 200 includes designing a scatterometry target having a non-polarizing structure (step 280) to have at least one additional target layer having at least one polarizing structure configured to produce a phase shift of 180° (step 280). , and designing the additional target layer(s) to be above and/or below the non-polarizing structure.

Advantageously, coupling the polarization control hardware (optical system 150) and the polarization target (target 100) provides an additional level of control of the diffraction order parameters. In target 100, a complementary layer or any available intermediate layer may be used to introduce a segmented dummy structure for the purpose of controlling or enhancing the measured polarization properties of the target. Combining a polarization control HW with a polarization target is known to increase the accuracy and precision of overlay measurements. Optical system 150 and target 100 may be implemented on a variety of metrology platforms and may enhance the ability to create targets, such as devices.

It is emphasized that the design principles disclosed herein can control the phase and/or amplitude of any diffraction order, thus providing additional advantages over zero-order cancellation.

Aspects of the present invention have been described above with reference to flowcharts and/or partial diagrams of methods, apparatus (systems) and computer program products according to embodiments of the present invention. It will be understood that each portion of the flowcharts and/or partial diagrams, and combinations of portions of the flowcharts and/or partial diagrams, may be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing device, such that the instructions executed by the processor of the computer or other programmable data processing device are shown in flowcharts and/or partial diagrams or portions thereof. A machine may be created to create means for implementing a specified function/action.

Further, these computer program instructions are stored on a computer readable medium, such that the instructions stored on the computer readable medium create an article of manufacture including instructions for implementing the functions/acts specified in the flowcharts and/or partial diagrams or portions thereof. It may instruct a computer, other programmable data processing apparatus, or other device to function in a particular way.

Computer program instructions may also be loaded into a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable apparatus, or other device, such that the instructions are executed on the computer or other programmable apparatus. Create a computer-implemented process to provide a process for implementing the functions/acts specified in the flowcharts and/or partial diagrams or portions thereof.

The foregoing flowcharts and diagrams illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products in accordance with various embodiments of the present invention. In this regard, each portion of a flowchart or partial diagram may represent a module, segment, or portion of code that includes one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions recited in the above sections may occur out of the order recited in the figures. For example, two portions shown in succession may in fact be executed substantially simultaneously, or may sometimes be executed in reverse order depending on the functions involved. Each part of the partial diagrams and/or flowcharts, and combinations of portions of the partial diagrams and/or flowcharts, may be implemented by special-purpose hardware-based systems, or combinations of special-purpose hardware and computer instructions, that perform specified functions or operations. You should also take note.

In the above description, an embodiment is an example or implementation example of the present invention. Various appearances of “one embodiment,” “an embodiment,” “certain embodiments,” or “some embodiments,” are not necessarily all referring to the same embodiments. it is not Although various features of the invention may be described in the context of a single embodiment, the features may also be provided individually or in any suitable combination. Conversely, while the invention may, for clarity, be described herein in the context of separate embodiments, the invention may also be embodied in a single embodiment. Certain embodiments of the invention may include features from different embodiments disclosed above, and certain embodiments may include elements from other embodiments disclosed above. The disclosure of elements of the invention in the context of a particular embodiment should not be construed as limiting its use in that particular embodiment alone. Moreover, it is to be understood that the invention may be practiced or practiced in various ways, and that the invention may be embodied in specific embodiments other than those briefly set forth in the above description.

The invention is not limited to these drawings or the corresponding description. For example, the flow need not move through each illustrated box or state or in exactly the same order as shown and described. The meanings of technical and scientific terms used herein will be commonly understood by one of ordinary skill in the art to which this invention belongs, unless otherwise defined. While the present invention has been described in connection with a limited number of embodiments, these should not be construed as limiting the scope of the invention, but rather as illustrative of some of the preferred embodiments. Other possible variations, modifications and applications are also within the scope of the present invention. Accordingly, the scope of the present invention should not be limited by what has heretofore been described, but rather by the appended claims and their equivalents.

Claims (24)

In the method,
A phase of 180° between the 0th order diffraction signals upon illumination of the scatterometry target by at least one of designing a scatterometry target and configuring an optical system of a metrology tool. enhancing a first order diffraction signal with respect to the zero order diffraction signal from the scatterometry target having a coarse pitch to produce a shift; and
configure the optical system of the metrology tool to illuminate the scatterometry target with two vertically polarized illumination components, and resolve the diffraction signal into two vertically polarized directions that complement the two vertically polarized illumination components (analyze), canceling the zero-order diffraction signal
how to include 2. The method of claim 1, further comprising designing the scatterometry target to have a polarizer at half the coarse pitch to produce a phase shift of 180°;
wherein the polarizer is configured to be vertically polarized. The method according to claim 1, further comprising the step of combining a first phase shift by a target design and a second phase shift by an optical system configuration, wherein the sum of the first phase shift and the second phase shift is 180° Way. 2. The method of claim 1, further comprising: designing the scatterometry target having a non-polarizing structure to have at least one additional target layer having at least one polarizing structure configured to produce the 180° phase shift. How to include. 5. The method of claim 4, wherein the at least one additional target layer is over the non-polarizing structure. 5. The method of claim 4, wherein said at least one additional target layer is under said non-polarizing structure. A scatterometry metrology target having a coarse pitch and configured to, upon illumination, produce a phase shift of 180° between zero-order diffraction signals, the target comprising:
a first portion of the coarsely pitched region is divided in one direction, a second portion of the coarsely pitched region is divided in a direction perpendicular to the direction of the first region, the target comprising an initial non-polarizing structure, and and at least one additional target layer having at least one polarizing structure configured to produce a phase shift of 180°. 8. The scatterometry metrology target of claim 7, wherein the polarizer is designed to have a polarizer at half of the coarse pitch to produce a phase shift of 180°, the polarizer configured to be vertically polarized. 9. The scatterometry metrology target of claim 8, wherein the polarizer is divided into fine pitches. 8. The scatterometry metrology target of claim 7, wherein the at least one polarizing structure is divided into fine unresolved pitches. The scatterometry metrology target of claim 10 , wherein the at least one polarizing structure is split along a direction perpendicular to a splitting direction of the initial non-polarizing structure. 8. The scatterometry metrology target of claim 7, wherein said additional target layer is over said non-polarizing structure. 8. The scatterometry metrology target of claim 7, wherein the additional target layer is below the non-polarizing structure. Illuminating an unpolarized scatterometry target by means of two vertically polarized illumination components and analyzing the resulting diffraction signal into two vertically polarized directions complementary to the two vertically polarized illumination components so that the scatter A metrology tool having an optical system configured to cancel a zero-order diffraction signal by configuring the illumination and the decomposition to produce a phase shift of 180° between identical zero-order diffraction signals from a lometry target. 15. The system of claim 14, wherein the optical system comprises: a polarizer and an analyzer, at least one wave plate, at least one polarizing beam splitter, and at least one neutral density (ND) to control the polarization of the illumination and the diffraction signal. A metrology tool comprising at least one of a filter. A measurement system comprising:
a scatterometry metrology target having a coarse pitch and configured to, upon illumination, produce a first phase shift between zero-order diffraction signals;
Illuminates the target by two vertically polarized illumination components and analyzes the resulting diffraction signal into two vertically polarized directions that complement the two vertically polarized illumination components, resulting in zero upon illumination of the target. Metrology tool having an optical system configured to create a second phase shift between difference diffraction signals
includes,
and the sum of the first phase shift and the second phase shift is 180° to cancel the zero-order diffraction signals. 17. The system of claim 16, wherein the optical system comprises at least one of a polarizer and an analyzer, at least one wave plate, at least one polarizing beam splitter, and at least one ND filter, for controlling the polarization of the illumination and the diffraction signal. A measurement system comprising a. 17. The metrology system of claim 16, wherein the first phase shift is 180° and the second phase shift is zero. 19. The metrology system of claim 18, wherein the scatterometry metrology target is configured to produce a phase shift of 180° between zeroth order diffraction signals upon illumination of the target. 20. The metrology system of claim 19, wherein the system is designed to have a polarizer at half the coarse pitch of the target to produce a phase shift of 180°, the polarizer configured to be vertically polarized. 17. The metrology system of claim 16, wherein the target comprises an initial non-polarizing structure and at least one additional target layer having at least one polarizing structure configured to produce the first phase shift. A scatterometry metrology target having a coarse pitch and configured to, upon illumination, produce a phase shift of 180° between a zero-order diffraction signal, the target comprising:
a first portion of the coarse pitched region is divided in one direction, a second portion of the coarse pitched region is divided in a direction perpendicular to the direction of the first region, and wherein the scatterometry metrology target is A scatterometry metrology target designed to have a polarizer at half the coarse pitch to produce a phase shift of 180°, the polarizer configured to be vertically polarized. 23. The scatterometry metrology target of claim 22, wherein the polarizer is divided into fine pitches. delete

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